Solving the Ozone Puzzle

Troposphere

• Layer where our weather takes place.

• Layer closest to the earth’s surface.

• Layer we breathe.

• Ozone is created here by static electricity and pollution.

• Ozone in this layer is “Bad Ozone”.

• Ozone in this layer causes breathing difficulties.

Stratosphere

• Second layer of the atmosphere (16-50 km off the earths surface).

• This is where we find the ozone layer (27-30 km).

• Ozone in this layer is considered “Good Ozone”

• The ozone here blocks harmful UVB (ultra-violet radiation B) thus protecting life.

Ozone Layer

• Ozone layer is a concentration of ozone molecules in the stratosphere.

• 90% of the planet’s ozone is in the ozone layer.

• Stratospheric ozone is a naturally-occurring gas that filters the sun’s UV radiation.

• Ozone makes up 0.01% of the atmosphere (part of the 1% other gases)

Problems with Ozone Reduction

• Diminished ozone layer allows more radiation to reach the Earth’s surface.

• Over exposure to UV rays can cause skin cancer, cataracts, and weakened immune systems. It will also lead to reduce crop yield and disruptions in the marine food chain.

Chemistry of Ozone

• Oxygen atom (O)—single atom—very unstable

• Oxygen molecule (O2)—two atoms joined together—stable

• Ozone molecule (O3)—three atoms joined together—stable

Making ozone in the Stratosphere………

• UV ray (energy) + O2 ----> O + O (unstable oxygen atoms)

• O2 + O O3

• So…..UV radiation helps to make Ozone!

Destroying ozone in the Stratosphere…..

• UV ray + O3 O2 + O

• A little amount of O3 absorbs a lot of UV radiation

“Hole” in the Ozone Layer

• 1984 Scientists discovered a “hole” in the ozone layer over Antarctica

• Size of the hole equaled the size of the United States and as deep as the height of Mt. Everest.

• Scientists found a decrease in O3 and an increase in Cl (Chlorine)

• They decided it was a result of CFC’s (cloro-flouro-carbons)

CFC’s

• Used for refrigeration and air conditioning, foam blowing agents=styrofoam and blow in insulation and industrial cleaning solvents.

• All CFC containing products released CFC’s into the air and they traveled up to the stratosphere (long time)

CFC’s Destroy Ozone

• UV ray + CFC Cl + CF• O3 + Cl ClO + O2

• UV ray + ClO Cl + O

• When Cl finally bonds with something else the cycle stops.

• One Cl can destroy tens of thousands of O3

Why is the “hole” over Antarctica?

• Winter winds circle the continent

• Creating “stale” air with ice crystals

• The Cl attaches to the ice crystals and they stay attached all winter

9Nacreous clouds near McMurdo, Ross Island, Antarctica on August 28, 2004. These

polar stratospheric clouds at 80,000 feet are the highest of all clouds. They only occur in the polar regions when the stratospheric temperature dips below 100 degrees below zero

Fahrenheit. They are also the site of chemical reactions that break down ozone in the upper atmosphere and contribute to the creation of the ozone hole above Antarctica.

(Zenobia Evans/National Science Foundation) #

Spring comes

• Weather warms up

• Ice crystals evaporate

• All the Cl that has been stored all winter is released

• Ozone layer is rapidly reduced forming a “hole”

Summer comes….

• Cl is used up and the “hole” repairs itself.